China's cancer-stricken Nobel laureate Liu Xiaobo is in a critical condition, his hospital said Monday, raising fears about his life after Western doctors said there was time to take him abroad.

The First Hospital of China Medical University in the northeastern city of Shenyang said Liu's tumour has grown, his liver is bleeding and he has kidney problems.

The hospital said in a statement on its website that it is preparing to take the 61-year-old democracy advocate into emergency care if necessary, adding that "Liu's family members have been informed of the above circumstances".

But human rights activists decried the hospital statement as a delay tactic to prevent Liu from getting his wish of going abroad, where they say he would be free to speak out.

File image of Liu Xiaobo. AP

The Germany embassy, meanwhile, voiced "deep concern" about the leak of a video showing a gaunt-looking Liu in his hospital bed while the German and American doctors talk to his wife, Liu Xia, and Chinese physicians.

Decrying a breach of doctor-patient confidentiality, the embassy said in a statement that "certain authorities have evidently made audio and video surveillance recordings" of the weekend visit "against the expressed wishes of the German side".

"It seems that security organs are steering the process, not medical experts. This behaviour undermines trust in the authorities dealing with Mr. Liu's case, which is vital to ensure maximum success of his medical treatment."

China has faced international pressure to grant its most prominent dissident complete freedom and let him leave the country since he was transferred from prison to the hospital after being diagnosed with terminal liver cancer in late May.

The two foreign cancer specialists examined Liu on Saturday and said Sunday he could still safely leave the country, contradicting their Chinese counterparts.

But US oncology expert Joseph Herman from the University of Texas' MD Anderson Cancer Center and German doctor Markus Buchler of Heidelberg University warned in a statement that "the medical evacuation would have to take place as quickly as possible".

The video shows one of the foreigners, apparently Buchler, telling Liu Xia that the Chinese doctors had made a "very nice gesture" by inviting them to help and that they "are very committed to the treatment of ... your husband".

Liu moves his head during the conversation while the American doctor strokes his wife's back.

Rights groups question motive

Human rights activists said the hospital's latest statement shows the government is dragging its feet.

Amnesty International's China researcher Patrick Poon said the government wants to avoid any embarrassments ahead of a key Communist Party congress later this year. The meeting is expected to boost President Xi Jinping's grip on power.

"Allowing Liu Xiaobo and his family to go abroad would risk giving Liu Xiaobo the opportunity to talk to media and other supporters about his views on China's human rights situation," Poon told AFP.

Hu Jia, a Beijing-based activist and friend of Liu's, said the statement may be in response to the foreign doctors' conclusions.

"This is a way of slowing down the process. It doesn't show the patient's situation has deteriorated to the point of falling off a cliff."

Hu voiced concerns that if there is further delay, Liu may fall into a coma and never go free.

Asked whether Liu would be allowed to leave the country, Chinese foreign ministry spokesman Geng Shuang told reporters: "This is not a diplomatic question. It's China's internal affairs. We oppose any country interfering with China's internal affairs using these so-called individual cases."

German government spokesman Steffen Seibert said Berlin hopes Beijing will make a "humanitarian gesture (for Liu) and his family."

For his wife

Liu was arrested in 2008 after co-writing Charter 08, a bold petition that called for the protection of basic human rights and reform of China's one-party Communist system.

He was sentenced to 11 years in prison in December 2009 for "subversion". At the Nobel Peace Prize ceremony in Oslo in 2010, he was represented by an empty chair.

Another dissident close to the family, Ye Du, said Liu Xiaobo wants to go abroad for the sake of his wife, Liu Xia, who has been under house arrest since 2010.

"It's his personal wish to go abroad, because Xiaobo is very clear about his current situation -- which is that if he doesn't get out now, then he has no way to obtain freedom for his beloved wife Liu Xia," he said.